1. Field of the Invention
This invention relates to a slide type valve that is used in, for example, a chemical test apparatus, an environmental analysis apparatus, or a biotechnology research instrument and that is applied to, for example, a small slide type solenoid valve capable of opening and closing flowpaths through which liquid specimens or liquid reagents flow or a small injection valve capable of performing switching between flowpaths.
2. Description of Related Art
Improvement in accuracy, improvement in testing speed, minimization of specimens and reagents, device downsizing, and so forth are the most important issues to be achieved in various analytical devices, such as a chemical test apparatus, an environmental analysis apparatus, and a biotechnology research instrument, and, as a result, a solenoid valve that controls fluids used in such analytical devices has been required to be improved in performance. In particular, the amount of change in internal volume caused by opening or closing a valve disc, i.e., the pumping volume exerts influence on a fine control operation of specimens or reagents resulting from the minimization of a valve, and therefore it is absolutely imperative to minimize or zero the pumping volume in order to increase the accuracy of the analytical devices.
Accordingly, as disclosed by Japanese Published Patent Application No. 2008-51148, A, the present applicant has proposed a slide type solenoid valve capable of having a pumping volume of zero, capable of being reduced in device size, capable of being produced at low cost, and capable of being easily controlled.
This slide type solenoid valve includes a flowpath forming member that has flowpaths, a slidable sealing plate that is disposed slidably with respect to the flowpath forming member at a position of the flowpaths of the flowpath forming member and that has a flowpath-opening port portion communicable with the flowpaths and flowpath-closing wall portions capable of closing the flowpaths, a return-to-origin means that returns the slidable sealing plate from an advanced position to an original position, and a solenoid that advances the slidable sealing plate from the original position to the advanced position. The slidable sealing plate opens and closes the flowpaths by means of the flowpath-opening port portion and the flowpath-closing wall portions in accordance with the original position and the advanced position, or performs switching between the flowpaths.
However, the flowpath forming member of the slide type solenoid valve is structured by horizontally arranging two intermediate plates side by side between a first flowpath forming member and a second flowpath forming member and by integrally uniting the first flowpath forming member, the second flowpath forming member, and the intermediate plates together by use of bolts and nuts. The disk-shaped slidable sealing plate and a square holding plate are structured to be disposed in a space that is defined between the two intermediate plates and that penetrates in the up-down direction. In other words, the disk-shaped slidable sealing plate is structured to be placed by the first and second flowpath forming members in a sandwich manner and be firmly fixed with the bolts and the nuts, and therefore, depending on the tightening force of the bolts and nuts, variation is liable to be caused in gap dimensions between the first and second flowpath forming members. Therefore, a conventional problem resides in the fact that the slidable sealing plate has difficulty in keeping the sealing pressure of the sealing plate at a constant level during manufacture, and is unsuitable for mass production.
Furthermore, in Japanese Published Patent Application No. 2009-2383, A, the present applicant has proposed a slide type solenoid valve capable of being reduced in device size, capable of being produced at low cost, and capable of being easily controlled.
This slide type solenoid valve is structured to include a flowpath forming member that has a first flowpath and an end surface in which a port of the first flowpath is formed, a slidable sealing member that is slidable on the end surface of the flowpath forming member and that has a second flowpath capable of communicating with and closing the port of the first flowpath, an elastic urging means that always applies an elastic pressing force onto the slidable sealing member from a direction perpendicular to the sliding direction of the slidable sealing member and that presses the slidable sealing member against the end surface, a return-to-origin means that returns the slidable sealing member to an original position while applying a return-to-origin force onto the slidable sealing member from a direction along the sliding direction of the slidable sealing member, and a solenoid that moves the slidable sealing member from the original position while applying a driving force onto the slidable sealing member in a direction opposite to that of the return-to-origin force of the return-to-origin means.
However, in this slide type solenoid valve, an elastic pressing force is exerted on the slidable sealing member by the elastic urging means from a direction perpendicular to the sliding direction. Therefore, although this slide type solenoid valve has the advantage of being capable of easily keeping the sealing pressure of the slidable sealing member at a constant level and hence being suitable for mass production, this slide type solenoid valve still has the problem of being liable to cause a great pressure loss in a fluid flowing through the flowpath because the second flowpath of the slidable sealing member is formed of a return flowpath.